| 摘要: | 抗胰島素激素(Resistin)為一種已知的脂肪細胞所分泌的細胞激素, 它會造成胰島素抗性作用,並扮演著調節能量平衡的角色。之前的文獻中已經找出許多會去調節resistin基因表現的轉錄因子以及其結合位﹐但是其調控機制仍然不清楚。FoxO1 (Forkhead/winged helix box gene,group O-1) 轉錄因子會受到胰島素調控將其磷酸化﹐去決定是否能在細胞核內作用。之前的研究中指出FoxO1與resistin隨著脂肪細胞分化的程度越好,兩者基因在脂肪細胞內皆會有改變﹐而FoxO1參與調控一些胰島素所調控的基因表現。胰島素又會抑制抗胰島素機速基因的表現。因此本論文假設FoxO1轉錄因子會參與脂肪細胞內抗胰島素激素基因表現的調控作用﹐實驗結果證明﹕(1) FoxO1,3,4與resistin 基因之表現確實在脂肪細胞分化的過程中,逐步升高。(2)轉染FoxO1-AAA與human resistin promoter(-819~+24 bp)在HEK 293T細胞株中。發現FoxO1隨著劑量增加而有負調控該啟動子的活性。 (3) 轉染FoxO1-AAA與human resistin promoter(-819~+24 bp)在NIH 3T3細胞株中。發現FoxO1隨著劑量增加而有負調控該啟動子的活性。由以上結果顯示,Foxo1調節human resistin promoter(-819~+24 bp)活性,不會因轉染細胞株不同而有差異性。 (4)FoxO1-AAA與以架構的三種(-3880~-55 bp,-1330~-55 bp,-990~-55 bp)共同轉染到HEK 293T細胞內,發現FoxO1-AAA均負調節三種mouse resistin promoter的活性。(5)野生型FoxO1,突變型FoxO1-AAA,以及FoxO1-H215R,分別與Human resistin promoter(-819~+24 bp)共同轉染到HEK 293,HEK 293T,或3T3細胞株中。皆發現是負調控該promoter活性。所以顯示FoxO1是間接性調控resistin promoter的活性。綜合以上的結果得知,FoxO1是負調節Human resistin promoter的活性。因為FoxO1-AAA與mouse resistin promoter共同轉染到 3T3細胞株中,FoxO1-AAA正調節該promoter 的活性(採自於學妹楊淑雅的實驗數據),所以FoxO1調節mouse resistin promoter的活性會因轉染不同細胞株而有所差異。 Resistin is also known as adipocyte secreted factor (ADSF) that plays potential role in insulin resistiance and homeostasis. Although resistin can be regulated by transcriptional factors, the action mechanism is still not clear. FoxO1 (Forkhead/winged helix box gene,group O-1) is a member of a family of nuclear transcriptional factors that can be regulated by insulin. It has been reported that FoxO1 and resistin genes express during adipocyte differentiation, and are negatively regulated by insulin. In this thesis,the hypothesis that FoxO1 regulates resistin gene expression was examined. The results were as follows. First, expression of FoxO1, FoxO3, FoxO4, and resistin genes were increased as 3T3-L1 adipocyte differentiation proceeded. Second, cotransfection of FoxO1-AAA with human resistin promoter (-819~+24) to HEK 293 or 293T cells indicated that FoxO1-AAA dose-dependently inhibited activity of human resistin promoter. Third, cotransfection of FoxO1-AAA with human resistin promoter (-819~+24) to NIH 3T3 cells indicated that FoxO1-AAA does-dependently inhibited activity of human resistin promoter. These results suggest the cell type-independent effect of FoxO1-AAA on human resistin promoter. Fourth, cotransfection of FoxO1-AAA with mouse resistin promoter (-3546~+165 bp, -1145~+165 bp, -805~+165 bp) to HEK 293 or 293T cells showed a downregulatory effect of FoxO1-AAA on mouse resistin promoter. Finally, both the wild type of FoxO1 and the mutant types of FoxO1-AAA and FoxO1-H215R downregulated human resistin promoter activity, indicating an indirect effect of FoxO1 on resistin gene. Taken together, FoxO1 downregulates human resistin promoter activity. Because FoxO1-AAA upregulated mouse resistin promoter activity in 3T3 cells, FoxO1 may regulate mouse resistin promoter activity in the cell type-dependent manner (adapted from susu). |
